Modem having separate modem engine and data access arrangement

ABSTRACT

A modem which is separated into two circuit boards. One board contains the modem engine, while the second board contains the codec and the DAA components. The two boards are connected using only properly isolated digital signals so that the modem engine board does not require certification, only the codec/DAA board requiring certification. The codec/DAA board is contained in a housing to provide proper high voltage protection.

This application is a continuation of application Ser. No. 727,283 filedOct. 9, 1996, U.S. Pat. No. 5,737,397, which is a continuation of Ser.No. 304,262 filed Sep. 12, 1994, abandoned, which is acontinuation-in-part of U.S. Pat. Ser. No. 07/973,625 filed Nov. 9, 1992now 5,428,671 and of Ser. No. 08/148,661, filed on Nov. 5, 1993, whichin turn is a continuation-in-part of Ser. No. 07/973,625, filed Nov. 9,1992 now U.S. Pat. No. 5,428,671 and Ser. No. 07/972,949 filed Nov. 6,1992, now abandoned.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to modems used in digital communications and moreparticularly to the arrangement of components forming the modem.

2. Description of the Related Art

As the computer market becomes more global, a manufacturer obviouslywishes to be in as many countries as possible to increase its marketshare and revenues. However, this internationalization has created anumber of problems in many areas. Everyone is familiar with the problemsof the different languages and there are various solutions to this setof problems. Another common problem is voltage differences for the AClines, but this is also a well known problem and can be readily handledby uainf different power supplies or ones that can handle multiple inputvoltages.

A lesser known area of international concern is in the modem area. Eachcountry has different telephone connections and different electricalstandards for the telephone interface. In the past, this has alwaysrequired certifying the entire modem for each country in which it is tobe sold. This has resulted in a tremendous logistical problem, andtherefore, lesser distribution of many modem products. It was not worththe time and effort to qualify a modem in many different countries eachtime there was a change to the modem design, as the entire qualificationprocess had to be repeated. This qualification problem either increasedthe cost of modems or limited the technology available. Therefore, thereis a need for a modem which can be easily upgraded without requiringrecertification with each upgrade.

SUMMARY OF THE INVENTION

A modem according to the present invention separates the modem into twoportions, a modem engine portion and a data access arrangement (DAA)portion. Only the DAA portion needs to be certified; the modem engineportion does not require certification. This allows the performance andcapabilities of the modem engine to be upgraded as desired. The upgradedmodem engine is then connected to the previously certified DAA portion.Thus, upgrades to the modem can be easily performed and recertificationis not required.

A modem according to the preferred embodiment places the host computerinterface, the modem microcontroller and the digital signal processing(DSP) components on the modem engine board. The DAA board includes thecodec and the remaining standard DAA components, such as ring detectionand hybrid circuitry. All interfaces between the DAA board and the basicmodem engine board are done using digital signals. No analog signalswhatsoever are transmitted and all digital signals either drive relaysor are provided as outputs of optoisolated components, except for thosedigital signals provided to and from the codec. Therefore, no analogsignals are transmitted from the board, only digital signals. Thecertification bodies do not have concerns with the transmission of thedigital signals, only with analog signals which are not properlyisolated. Therefore, with a modem designed according to the presentinvention, the certification bodies require qualifying only the DAAboard containing the DAA components and the codec and do not requirerecertifying the modem engine board with each change to the componentson the modem engine board.

Further, the DAA board is contained and fully encapsulated in a housing,preferably a plastic housing, so that all of the high voltage circuitsare not accessible to the user without destruction of the housing.Therefore, the various safety bodies also are satisfied with the design.

Therefore, by the use of a modem with the components arranged inseparate circuit boards as indicated according to the present invention,international certification is required of only a limited component set,with changes to the remaining components being made freely and notrequiring certification.

BRIEF DESCRIPTION OF THE DRAWINGS

A better understanding of the present invention can be obtained when thefollowing detailed description of the preferred embodiment is consideredin conjunction with the following drawings, in which:

FIG. 1 is a block diagram of a computer system incorporating a modemengine according to the present invention;

FIG. 2 is a block diagram of the modem engine of FIG. 1;

FIG. 3 is a block diagram of a codec/DAA board for use with the modemengine of FIG. 2, and for installation and use with the computer systemof FIG. 1;

FIG. 4 is a perspective view of the housing for the codec/DAA circuitboard; and

FIG. 5 is a top view of the circuit board of the codec/DAA board forinstallation in the housing of FIG. 4.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

A computer system C incorporating a modem according to the presentinvention is shown in FIG. 1. The computer system C includes a processorsystem 10 such as simply a microprocessor, such as an Intel® 486 orPENTIUM, or a more complete processor system including a microprocessor,a cache controller and other components. The processor system 10 isconnected to a host bus 12 for communications. A memory system 14 isconnected to the host bus 12, as is a video system 16. A bus controller18 is connected between the host bus 12 and an input/output bus 20 suchas an EISA/ISA bus. An integrated system peripheral (ISP) 22, whichcontains numerous system elements such as a DMA controller, an interruptcontroller and so on, as is conventional, is connected to both the hostbus 12 and EISA/ISA bus 20. A series of slots 24 for receivinginterchangeable circuit cards are also provided on the EISA/ISA bus 20.A set of transceivers and latches 26 are connected between the EISA/ISAbus 20 and an X bus 28. Logically, the X bus 28 is identical to theEISA/ISA bus 20, but is provided as a separate bus for electricalloading reasons. Connected to the X bus 28 are various components whichare conventionally located on the system board of the computer system C.These include the read only memory (ROM) 30, which provides the BIOS andother system level instructions and an 8042 keyboard controller 32,which is connected to a keyboard port 34 and an auxiliary or pointingdevice port 36. A real time clock (RTC) 38 is connected to the X bus 28,as is a multiple peripheral component (MPC) 40. The multiple peripheralcomponent 40 includes a parallel port 42 and two serial ports 44 and 46used for communications purposes. Of interest in this description, amodem engine 48 is also connected to the X bus 28. The modem 48 isconnected to a codec/DAA connector 49.

The computer system of FIG. 1 is exemplary and numerous other computersystem designs could be used. Further the modem engine 48 can be locateddirectly on the EISA/ISA bus 20 or other similar bus or couldalternatively be located directly on the host bus 12. The exact locationis not critical to the present invention. Preferably, in the preferredembodiment, all of the components illustrated in FIG. 1 are located on asingle circuit board, so that the modem engine 48 is integrated in thecomputer system C. Further, though not as preferable, the modem engine48 could be an external device connected to a serial port 44 or 46.

Proceeding now to FIG. 2, the modem engine 48 is shown in more detail. Ahost interface block 100 is connected to the XA and XD lines 102 and 104which form the address and data portions of the X bus 28. The controlsignals are similarly connected to portions of the X bus 28 but are notshown for simplicity. The host interface 100 is used to provide theprimary interface to the processor 10 as is conventional for modemoperations. Therefore, the host interface 100 conforms to theconventional UART definitions and is designed to be located at theconventional address locations.

The XA bus 102 and XD bus 104 are also connected to a microcomputer 106to allow direct access to certain functions of the microcomputer 106.Additionally, the microcomputer 106 is connected to the host interface100 via certain designated control pins to allow control of functions ofthe host interface 100. Additionally, a memory data bus 108 and a memoryaddress bus 110 are provided from the microcomputer 106 for accessingexternal memory devices and memory-mapped I/O devices. A memory controlbus is also provided, but is not shown for simplicity. These externalmemory devices include a ROM 112 which includes the operatinginstructions for the microcomputer 106 and a RAM 114 which providesadditional memory with the microcomputer 106. The host interface 100 isa memory-mapped I/O device, and thus connected to the memory address bus110 and the memory data bus 108, to allow high speed communicationsbetween the microcomputer 106 and the host interface 100. In addition, aDSP interface 116, as is well known, is connected to the memory data bus108 and the memory address bus 110 to allow parallel formatcommunication between the microcomputer 106 and the DSP interface 116.The DSP interface 116 is connected to the DSP or digital signalprocessor chip 118 which performs the calculations to provide desiredmodem functions. The DSP 118 is a conventional unit such as the DSP 16 aprovided by AT&T. The DSP interface 116 is preferably the companion chipto the DSP 118. The DSP interface 116 and the DSP 118 provide the datapump for the modem engine 48. The microcomputer 106 is preferably aconventional 8 bit microcomputer.

Certain interface signals are necessary to connect the modem engine 48to the codec/DAA board 200 (FIG. 3). Referring then to FIG. 3 to helpcomplete the description of FIG. 2, the codec/DAA circuit board 200components are shown. These include a codec 120 designed to cooperatewith the DSP 118. It is noted that the codec/DAA board 200 is shown insimplified format and certain detailed components are not shown tosimplify the illustration. The detailed components are well known tothose skilled in the art. The codec 120 provides an RXA or receiveanalog signal to an amplifier 122 and receives a TXA or transmit analogsignal from an amplifier 124. The output of the amplifier 122 and theinput of the amplifier 124 are connected together and to one terminal ofa first side winding of a hybrid transformer 126 as commonly used intelephone connections. The second terminal of the first side winding isconnected to ground.

An RJ-11 jack 128 is provided to receive certain telephone signals, suchas TIP and RING as conventionally used, and to provide TIPT and RINGTsignals to a connected telephone handset. The jack 128 receives anadapter cable (not shown) to allow connection to the telephone line andto allow connection of an external telephone set. Preferably, the TIPand RING signals are provided from the RJ-11 jack 128 to the commonpoles of a two pole, two position, relay 130. The relay 130 has one coilterminal connected to a +5V signal, and the second terminal connected tothe emitter of a PNP transistor 132, whose collector is connected toground. The base of the transistor 132 is connected through a pull-upresister 134 to +5V and receives the DV₁₃RLY* or device relay invertedsignal. Thus, if the DV₁₃RLY* signal is provided high or is not present,the TIP signal is normally connected to the TIPT signal, and similarly,the RING signal is normally connected to the RINGT signal. In thismanner, when the DV₁₃RLY* signal is disabled or in the high state, therelay 130 is disabled and the TIP and RING signals are provided back tothe RJ-11 jack 128 to the external telephone set to allow it to beutilized.

If the modem is to be utilized, the relay 130 is activated by taking theDV₁₃RLY* signal to a low level, activating the transistor 132, so thatthe TIP and RING signals are then provided to TIPI and RINGI or TIPinternal and RING internal signals. An MOV protection device 135 isconnected between the TIPI and RINGI signals for circuit protection. TheTIPI signal is coupled to one terminal of the second side winding of thetransformer 126, while the second terminal of the second side winding ofthe transformer 126 is coupled through a pair of reverse seriesconnected Zener diodes 136 and 138 to the RINGI signal. An off hookrelay 140 is connected across the diodes 136 and 138, so that when theoff hook relay 140 is activated, a short circuit is formed around thediodes 136 and 138, so that the second terminal of the second sidewinding of the transformer 126 is then directly connected to the RINGIcircuit, thus placing the modem off hook. One side of the coil on theoff hook relay 140 is connected to ground, with the other side connectedthrough a pull-up resistor 142 and a PNP transistor 144 to a +5 voltsignal. An OH₁₃RLY* signal is provided to the base of the transistor 144to select whether the modem is on hook or off hook. When the OH₁₃RLY*signal is low, the off hook relay 140 is activated and the modem is offhook.

Certain signals also need to be provided from the codec/DAA board 200 tothe modem engine 48. These include a ring indication or RI* signal whichis provided at the collector of an NPN transistor 202 contained in anoptoisolator 204. The emitter of the transistor 202 is connected toground, with the collector pulled up to +5 volts via a pull-up resistor206. A pair of parallel, opposed diodes 208 and 210 are contained in theoptoisolator 204 to provide light to the base of the transistor 202. Thediodes 208, 210 are coupled between the TIPT and RINGT signals by theuse of a series capacitor 209 and resistor 211 and reverse seriesconnected Zener diodes 213 and 215. In this way, the ring indicatoroptoisolator 204 provides the RI* signal only when voltage is sufficientto indicate a ring voltage is present. As the optoisolator 204 ispresent, the RI* signal is positively separated or decoupled from theanalog signals as necessary for certification purposes. Similarly, theuse of the relays 130 and 140 provide similar isolation for outputsprovided from the modem engine 48.

The RINGT signal is passed through a pair of parallel, opposed diodes220 and 222 in an optoisolator 224 so that should current flow in theRINGT signal conductor, the diodes 222 and 220 provide light to the baseof an NPN transistor 226 contained in the optoisolator 224. Thecollector of the transistor 226 is connected to +5V and the emitter isconnected to ground by a resistor 228. The emitter of the transistor 226provides the LCS or loop current signal to indicate that loop current isbeing drawn, indicating that the external telephone set connected to theRJ-11 connector 128 is off hook. By monitoring the LCS signal, the modemengine 48 will not cause the modem to go off hook while the externaltelephone set is in use.

The codec 120 is connected to the DSP 118 by four signals referred to asRXD, TXD, SYNC and CLK. The RXD and TXD signals are the receive andtransmit digital signals, while the SYNC and CLK signals areconventional signals as utilized between a DSP 118 and a codec 120.

Additionally, a serial EEPROM device 250 is located on the codec/DAAboard 200 to provide country code configuration data, as the actualcomponents and requirements of the codec/DAA board 200 vary from countryto country. The use of the EEPROM 250 allows the microcontroller 106 tooperate properly in each country. Two signals, a CLKT and a DATAT areprovided to serial EEPROM 250.

All of the signals connecting the codec/DAA board 200 to the modemengine 48 are provided to a connector 149, which can be directlyconnected to the connector 49 or can be connected by use of a cable withappropriate mating connectors.

Referring back to the modem engine 48 of FIG. 2, the CLKT and DATATsignals are connected to the microcomputer 106 to allow it tointerrogate the serial EEPROM 250 to determine the specific country forwhich the codec/DAA module 200 is designed. The DV₁₃RLY* signal isprovided from the microcomputer 106. In addition, miscellaneous outputcontrol signals are provided by the microcontroller 106 for alternateembodiments of the codec/DAA module 200. In alternate embodiments usedin different countries, it is desirable to have additional features, andtherefore, these features are activated by the microcomputer 106 by theuse of the miscellaneous output control signals. The outputs can includea DET₁₃RLY* signal used to control circuitry to provide a secondary loopcurrent detector when off hook in voice mode when an external telephoneset is in use as required in certain countries, an EARTH₁₃RLY* signalused with a relay to connect the TIP or RING signals to ground torequest dial tone in certain countries, a SHUNT₁₃RLY* signal used withproper circuitry to provide proper DC characteristics as necessary insome countries, HYB₁₃CTL1 and HYB₁₃CTL2 signals used to cause inclusionof additional components to improve hybrid matching or intentionalunmatching, and a CALLER₁₃ID* signal used to activate circuitry to allowAC coupling to the TIP or RING signals to provide snooping withoutdrawing AC current as necessary for the caller ID function. All of thesesignals are connected to relays to provide the proper isolation.

The RI* or ring indication signal is provided from the codec/DAA board200 to the DSP interface circuitry 116, as is the LCS signal. Similarly,the OH₁₃RLY* signal is provided from the DSP interface 116.

Therefore, it can be seen that all of the connections between the modemengine 48 and the codec/DAA module 200 are digital only and the controlsignals and feedback signals have been isolated either by mechanicalrelays or by optoisolators.

An earlier attempt to resolve the certification problem was tried in theSpeedPaq 14.4 K modem manufactured by Compaq Computer Corporation. Thatmodem was designed for application inside a notebook computer. Knowingthis international certification problem, the modem was designed as twoseparate circuit boards, one containing the basic modem engine, andRJ-11 and RJ-45 jacks, the second one including the parts for the DAA.The SpeedPaq 14.4 K differed from the preferred embodiment describedabove in that the codec was located on the same circuit board as theremainder of the modem engine components. As a result, TXA and RXA orthe analog transmit and receive signals were provided over theconnectors between the boards. Further, the TIP and RING signals wereprovided to the modem engine board to connect to the RJ-11 jack. Uponapplication to the certification bodies, it was determined that thetransmission of these two analog signals to the modem engine board andthe TIP and RING signal transmission was sufficient to requirequalification, and thus requalification, of that board. Thus, while theSpeedPaq 14.4 K was a first step, it was not completely successful insolving the recertification problem.

In contrast, only digital signals are transmitted between the two boardsin the preferred embodiment, and therefore, the various nationalcertification bodies have not required certification of the modem engine48, only the codec/DAA board 200. This means that only the codec/DAAboard 200 needs to be certified for each particular country and thatchanges to the modem engine 48 and to the computer system C in which themodem engine 48 is contained can be readily made without requiringrecertification of the modem engine 48.

FIG. 4 is an illustration of the preferred embodiment of the housing Hwhich contains the codec/DAA board 200. The housing H preferably isformed of plastic to provide necessary voltage protection and is formedof two pieces snapped together or seamlessly welded together usingplastic welding techniques as is well known so that the housing H cannotbe easily opened without destruction by the user. Thus, the housing Hprovides the necessary high voltage protection as required by the safetybodies. This high voltage protection had been a problem with the earlierSpeedPaq 14.4 K modem, as the high voltage components were notindependently shielded. The housing H contains a first opening 300 toreceive the RJ-11 jack 128 necessary for connection to the telephoneline, and two openings (not shown) to receive a connector cable from themodem engine 48. The arrangement of the connector cable can be morereadily seen in FIG. 5 which is an illustration of the circuit board ofthe codec/DAA module 200. As can be seen, the RJ-11 jack 128 is providedat one end for provision through opening 300 and two parallel wiredconnectors 302 and 304, which correspond to connector 149, are providedfor alternate physical arrangements of the housing H. A cable (notshown) connects one of the connectors 302 or 304 to the connector 49.

Therefore, a modem according to the present invention is divided intotwo portions and connected only using properly isolated digital signals.In this manner, all of the components necessary for certification can beplaced in one portion and the remaining modem engine components placedon a board not requiring certification, allowing easy upgrading forimproved performance of the modem.

The foregoing disclosure and description of the invention areillustrative and explanatory thereof, and various changes in the size,shape, materials, components, circuit elements, wiring connections andcontacts, as well as in the details of the illustrated circuitry andconstruction and method of operation may be made without departing fromthe spirit of the invention.

What is claimed is:
 1. A modem comprising: a modem engine moduleincluding at least one integrated circuit chip mounted on a firstcircuit board; a data access arrangement (DAA) module including at leastone other integrated circuit chip mounted on a second circuit board, thesecond circuit board being separate from the first circuit board; and aconnector between the modem engine module and the DAA modules, theconnector including a plurality of conductive lines electricallyconnecting electrical signal nodes in the modem engine module withelectrical signal nodes in the DAA module, each and every one of theelectrical signal nodes being one of a digital signal node or a powersupply node.
 2. The modem of claim 1 wherein the modem engine modulecomprises: a microcontroller; and; a data pump coupled to themicrocontroller.
 3. The modem of claim 1 wherein the DAA modulecomprises: a codec; and a telephone line interface coupled to the codec.4. The modem of claim 1 wherein the DAA module is contained in anenclosed housing.
 5. The modem of claim 1 wherein the modem enginemodule comprises: a computer system interface; a microcontrollerconnected to the computer system interface, the microcontrollerproviding first digital control signals; and a data pump providingsecond digital control signals and receiving first data signals; whereinthe computer system interface, said microcontroller, said data pump andsaid first connector are located on the first circuit board; and whereinthe connector is connected to said microcontroller and said data pumpfor transferring said first digital control signals from saidmicrocontroller, said second digital control signals from said datapump, and said first data signals to said data pump.
 6. The modem ofclaim 1 wherein the DAA module comprises: a codec for receiving seconddigital control signals from the connector and providing first datasignals to the connector; and circuitry configured for connection to atelephone line for receiving first digital control signals from theconnector, for receiving telephone line signals from the telephone line,and for providing said telephone line signals to said codec; wherein thecodec and the circuitry are located on the second circuit board; andwherein the connector transfers said first digital control signals andsaid second digital control signals from modem engine module andtransfers the first data signals to the modem engine module.
 7. Acomputer system comprising: a processor coupled to a first bus; a memorysystem coupled for access by the processor; a bus interface circuitcoupled between the first bus and a second bus; a keyboard controllercoupled for access by the processor; and a modem coupled for access bythe processor, the modem including: a modem engine portion including atleast one integrated circuit chip mounted on a first circuit board; adata access arrangement (DAA) portion including at least one otherintegrated circuit chip mounted on a second circuit board, the secondcircuit board being separate from the first circuit board; and aconnector between the modem engine portion and the DAA portion, theconnector including a plurality of conductive lines electricallyconnecting electrical signal nodes in the modem engine portion withelectrical signal nodes in the DAA portion, each and every one of theelectrical signal nodes being one of a digital signal node or a powersupply node.
 8. The system of claim 7 wherein the modem engine isconnected to the second bus.
 9. The system of claim 7 wherein the businterface circuit and the keyboard controller are located on the firstcircuit board.
 10. The system of claim 7 wherein the modem engineportion comprises: a computer system interface; a microcontrollerconnected to the computer system interface, the microcontrollerproviding first digital control signals; and a data pump providingsecond digital control signals and receiving first data signals; whereinthe computer system interface, said microcontroller, said data pump andsaid first connector are located on the first circuit board; and whereinthe connector is connected to said microcontroller and said data pumpfor transferring said first digital control signals from saidmicrocontroller, said second digital control signals from said datapump, and said first data signals to said data pump.
 11. The system ofclaim 7 wherein the DAA portion comprises: a codec for receiving seconddigital control signals from the connector and providing first datasignals to the connector; and circuitry configured for connection to atelephone line for receiving first digital control signals from theconnector, for receiving telephone line signals from the telephone line,and for providing said telephone line signals to said codec; wherein thecodec and the circuitry are located on the second circuit board; andwherein the connector transfers said first digital control signals andsaid second digital control signals from modem engine portion andtransfers the first data signals to the modem engine portion.
 12. Thesystem of claim 7 wherein the DAA module is contained in an enclosedhousing.
 13. The system of claim 7 wherein the second bus comprises anEISA bus.
 14. A modem for use with a computer system to allowcommunication over a telephone line, the modem comprising: a modemengine portion, said modem engine portion comprising: a computer systeminterface; a microcontroller connected to said computer systeminterface, said microcontroller providing first digital control signals;a data pump providing second digital control signals and receiving firstdata signals; a first connector providing electrically conductive pathscoupled to said microcontroller and said data pump for transferring saidfirst digital control signals from said microcontroller, said seconddigital control signals from said data pump, and said first data signalsto said data pump; and a first circuit board on which said computersystem interface, said microcontroller, and said data pump are located;and a data access arrangement portion, said data access arrangementcomprising: a second connector providing electrically conductive pathsconnected to electrically conductive paths of said first connector fortransferring said first digital control signals and said second digitalcontrol signals from said first connector and for transferring saidfirst data signals to said first connector; a codec for receiving saidsecond digital control signals from said second connector and providingsaid first data signals through conductive paths to said secondconnector; circuitry configured for connection to the telephone line forreceiving first digital control signals from said second connector, forreceiving telephone line signals from said telephone line, and forproviding said telephone line signals to said codec; and a secondcircuit board on which said codec and said circuitry are located,wherein said first circuit board and said second circuit board areseparate circuit boards.
 15. The modem of claim 14 wherein said dataaccess portion is contained in an enclosed housing to provide highvoltage protection.
 16. The modem of claim 14 wherein said data accessarrangement circuit includes a plurality of relays receiving said firstand second digital control signals from said modem engine portion andincludes a plurality of optoisolators to provide digital control signalsto said modem engine portion.
 17. The modem of claim 14 wherein saidfirst connector comprises a first circuit board connector located on thefirst circuit board and said second connector comprises a second circuitboard connector located on the second circuit board.
 18. A modemcomprising: a modem engine module including at least one integratedcircuit chip mounted on a first circuit board; a data access arrangement(DAA) module including at least one other integrated circuit chipmounted on a second circuit board, the second circuit board beingseparate from the first circuit board; and a connector between the modemengine module and the DAA modules, the connector including a pluralityof conductive lines providing electrically conductive signal pathsbetween electrical signal nodes in the modem engine module andelectrical signal nodes in the DAA module, each and every one of theelectrical signal nodes being either a digital signal node or a powersupply node.
 19. The modem of claim 18, wherein said connector comprisesfirst and second detachable portions.
 20. A modem comprising: a modemengine module including at least one integrated circuit chip mounted ona first circuit board; a data access arrangement (DAA) module includingat least one other integrated circuit chip mounted on a second circuitboard, the second circuit board being separate from the first circuitboard; and a connector between the modem engine module and the DAAmodules, the connector providing only digital signal connections andpower supply connections between the modem engine module and the DAAmodule.
 21. The modem of claim 20, wherein the connector comprises afirst circuit board connector located on the modem engine module and asecond circuit board connector located on the DAA module, and wherein atleast one of said first and second circuit board connectors is locatedadjacent an edge of the module on which that circuit board connector islocated.
 22. A modem comprising: a modem engine module including atleast one integrated circuit chip mounted on a first circuit board; adata access arrangement (DAA) module including at least one otherintegrated circuit chip mounted on a second circuit board, the secondcircuit board being separate from the first circuit board; and aconnector between the modem engine module and the DAA modules, theconnector including a plurality of electrically conductive paths andproviding no analog signal connections between the modem engine moduleand the DAA module.
 23. The modem of claim 22, wherein said connectorcomprises first and second detachable portions.